Many internet message protocols such as Internet Message Access Protocol (IMAP), ActiveSync® by Microsoft Corporation, and Instant Messaging—Presence (IM) were originally designed for use with wired networks. The protocols require a TCP connection between the message server and the client to perform any activity such as reception of a new email or a presence status update of a buddy in a social network environment. To maintain the TCP connection, the client must keep the IP address alive. IP-based wired networks are tolerant of large timeouts. Thus, in wired networks, it is not difficult for Internet message protocols to maintain TCP connections for a long period of time.
Most internet message retrieval protocols use a polling based scheme to detect arrival of new messages. The polling interval is configurable and is set as part of an application-level message. For example, ActiveSync® uses a custom HTTP method called “PING” and sets a timeout value as part of the method. All of these application-level messages ride on top of the TCP layer. Thus, the messages require the underlying TCP to be kept alive for the duration of the timeout value. Typical values for an application polling timeout period is between 15 and 60 minutes.
Due to the transient nature of wireless networks, there are many possibilities for the loss of a TCP connection at any point in time. TCP connections may be torn down due to handoff, signal loss, etc. In order to resume message retrieval polling, a new TCP connection must be established. Establishing the new TCP resets the polling interval. Wireless devices supporting these protocols will re-establish a TCP connection whenever it is lost. In the re-establishment procedure, the IP address of the device may change. In many cases, the polling method must be established and re-established several times per hour. This activity has an adverse impact on battery life.